Abstract Objective: To evaluate the pattern of use of opioid and other illegal drugs in patients seeking addiction treatment in Birjand, eastern Iran. Methods: The prospective study was conducted from March 21, 2009 to March 21, 2010, and comprised all patients referred to the seven addiction treatment centres in Birjand. Data was obtained through pre-designed questionnaires and it was analysed using SPSS 16. Results: Of the 700 substance users referred to the 7 centres and who volunteered to participate, 632 (90.3%) were males and 68 (9.7%) were females. The male/female ratio was ~ 9.3/1. Mean age was 34±10.2 (range: 10-75) years. The type of drugs used included traditional drugs (n= 342; 48.9%) and newer modern drugs (n=314; 44.9 %). The mean age of the first experience with drugs was 21.91±7.1 (range=0-60) years. There was significant different between the type of drugs used and the place of residence (p